The present invention relates to a stage unit and its making method, and an exposure apparatus and its making method, and, more specifically, a stage unit which controls the position of a sample placed on itself and its making method, and an exposure apparatus which is equipped with the stage unit and transfers a predetermined pattern onto a wafer, and its making method.
In a lithography process for making a semiconductor device, liquid crystal display device, or the like, an exposure apparatus has been used. In such an exposure apparatus, patterns formed on a mask or reticle (to be generically referred to as a xe2x80x9creticlexe2x80x9d hereinafter) are transferred through a projection optical system onto a substrate such as a wafer or glass plate (to be referred to as a xe2x80x9csubstratexe2x80x9d or xe2x80x9cwaferxe2x80x9d hereinafter, as needed) coated with a resist, etc. As apparatuses of this type, a static exposure type projection exposure apparatus, e.g., a so-called stepper, and a scanning exposure type projection exposure apparatus, e.g., a so-called scanning stepper are mainly used. Such an exposure apparatus is equipped with a stage unit, which is movable in two-dimensional directions while holding a wafer, to transfer a pattern formed on a reticle onto a plurality of shot areas on the wafer in turn.
In such a stage unit, the wafer is held on a wafer holder by vacuum chucking, etc. and fixed on a wafer table (movable body) to set the position of the wafer to a exposure position with high accuracy. Such wafer tables have been driven along a mechanical guide surface by a driving unit mechanically in contact with the wafer table and movable. Therefore, stage units have been equipped with X-stage to drive the wafer table in X direction and Y-stage to drive the wafer table together with X-stage in Y direction to move the wafer table on the X-Y plane.
Meanwhile, the development of a stage unit which controls the position of a wafer with high accuracy without being affected by the mechanical accuracy, etc. of a guide surface and performs positioning of the wafer by supporting a flat-plate-like shaped and movable body, on which the wafer is placed above a supporting member, by levitation and driving the movable body in a non-contacting manner to avoid mechanical friction and prolong the life of the stage is in progress. As such stage units, a variable magnetic reluctance driving method in which a linear pulse motor, as in a Sawyer motor, using the variable magnetic reluctance driving method is so structured that two axes are combined with each other, and a stage unit using a planar motor as a driving unit (driver) employing a Lorentz (electromagnetic) force method disclosed in, for example, Japanese Patent Laid-Open No. 58-175020 and U.S. Pat. No. 5,196,745 have been suggested.
Recently, wafers on which patterns are transferred by an exposure apparatus are being enlarged. Along with the enlargement of wafers, a wafer table as a table on which a wafer is placed is also enlarged and necessarily the weight of the wafer table is increased. Therefore it is necessary to drive the wafer table by a large force to move the wafer at high speed for the improvement of the through-put of the exposure apparatus.
Incidentally on driving the wafer table, the wafer table and a mover are moved together as one entity against a stator using a driving unit comprising the mover and the stator and on this occasion, a reaction to the force applied to the mover is induced in the stator. As a consequence, a vibration occurs and is transmitted to other members when the mover is mechanically connected with other members of the exposure apparatus, and then inflicts a bad effect on exposure accuracy. For example, when the mover is mechanically connected with a supporting member with respect to a projection optical system of the exposure apparatus, the projection optical system will vibrate and cause the degradation of the exposure accuracy.
Such a bad effect to the exposure accuracy generally becomes severer along with the increase of drive force of the mover. Therefore along with the enlargement of wafers, the mover is driven by a large force to move the wafer at high speed for the improvement of the through-put and the exposure accuracy will be degraded remarkably. That is, along with the enlargement of wafers it is getting difficult to improve both the through-put and the exposure accuracy.
The present invention has been made in view of the condition above. A first object of the present invention is to provide a stage unit that can move a placed sample at high speed and perform accurate positioning.
Also, a second object of the present invention is to provide an exposure apparatus that can improve both the through-put and the exposure accuracy by high speed movement of a substrate and highly accurate positioning.
From a first aspect, the present invention is a stage unit that is equipped with a driving unit including a mover and a stator; and a reaction canceling mechanism to apply to the stator a force canceling a reaction acting on the stator by electromagnetic interaction. This stage unit is referred to as a xe2x80x9cfirst stage unit of the present inventionxe2x80x9d hereafter.
According to the present invention, the reaction canceling mechanism generates a force to cancel the reaction acting on the stator by using electromagnetic interaction excellent in controllability and linearity and applies it to the stator, thereby accurately canceling the reaction acting on the stator. Accordingly, even with the increase of the drive force of the mover, the vibration of the stator is prevented and the stage unit is capable of high accurate positioning while moving a sample placed on itself.
In the first stage unit of the present invention, if the reaction canceling mechanism can apply to any arbitrary point of the stator a force having an arbitrary magnitude and an arbitrary direction, the reaction canceling mechanism may generate one kind of force and apply it to an appropriate point (for example, applying a force having the same magnitude as the reaction and opposite direction to the point of reaction application of the stator) to cancel a reaction caused by driving the mover translationally. However, when the stator is rotationally driven or the point of the stator to which the reaction canceling mechanism applies the force is fixed, it is generally impossible to cancel the reaction just by giving the stator one kind of force.
Therefore, in the first stage unit of the present invention, it is preferred for the reaction canceling mechanism to generate a force to act on at least two points of the stator and cancel the reaction as a whole. In this case, if the reaction canceling mechanism can apply forces having an arbitrary magnitude and an arbitrary direction to at least two fixed points of the stator, the reaction acting on the stator by a translational driving, a rotational driving or the combination of the both can be canceled. Especially, when the reaction acting on the stator is a force along a predetermined plane, the reaction can be canceled by applying two kinds of forces being along the predetermined plane and having magnitude and direction corresponding to the reaction.
The aforementioned case shows a case where the reaction canceling mechanism can apply the force having an arbitrary magnitude and an arbitrary direction to the stator. However, in a case where the points of the stator to which the reaction canceling mechanism applies the forces are fixed and the direction of the force applied to each point is predetermined, the reaction generally can not be canceled just by applying two kinds of forces to the stator. In such a case, the reaction canceling mechanism generates forces having respective predetermined directions, which cancel the reaction as a whole, and applies them to at least three points of the stator, thereby being able to cancel the reaction acting on the stator by a translational driving, a rotational driving or the combination of the both. Especially, if the reaction acting on the stator is a force along a predetermined plane, the reaction can be canceled by the reaction canceling mechanism applying three kinds of forces having magnitudes corresponding to the reaction and predetermined directions not parallel to each other, which are applied on three fixed points of the stator and are along the predetermined plane.
In the first stage unit of the present invention, the driving unit can be so structured that the drive force of the mover is generated by electromagnetic interaction. In such a case, as described above, the reaction acting on the stator on driving the mover can be accurately identified before driving the mover by generating the drive force for the mover by using electromagnetic interaction excellent in controllability and linearity. Therefore, the reaction acting on the stator can be canceled with high response-speed and accuracy by the reaction canceling mechanism applying a force to cancel the reaction acting on the stator to the stator in a manner like feed-forward simultaneously with driving the mover. That is, the stator appears to be free from the reaction.
The driving unit which generates the drive force for the mover by electromagnetic interaction is so structured that, for example, the stator has an armature unit including a plurality of armature coils, which are arranged in the shape of a matrix in a predetermined plane and have current paths almost parallel to the predetermined plane, and the mover has a driving magnetic pole unit to generate a magnetic flux having a direction crossing the predetermined plane.
In the first stage unit of the present invention equipped with this driving unit, the reaction canceling mechanism is so structured that reaction canceling magnetic pole units to generate a magnetic flux having a direction crossing the current paths of armature coils disposed on four corners of the armature unit and a control system that controls the direction and amplitude of currents supplied for the armature coils disposed on four corners of the armature unit are equipped. In this case, by the control system controlling the direction and amplitude of currents supplied for the armature coils disposed on four corners of the armature unit and the electromagnetic interaction between magnetic field induced by the magnetic pole units and the currents flowing in the armature coils disposed on four corners of the armature unit, the force canceling the reaction is applied to the stator along the same predetermined plane as the plane that the reaction is along. Accordingly, four forces along a predetermined plane, which have respective predetermined directions in the four fixed points of the stator and have magnitudes corresponding to the reaction, are applied with good controllability and the reaction can be canceled very accurately.
Incidentally, when applying to the stator the force to cancel the reaction acting on the stator on driving the mover, the reaction eventually comes to act on the reaction canceling magnetic pole units. It is preferred that the reaction canceling magnetic pole units and the stator are mechanically independent from each other to prevent the vibration from transmitting to the stator by the reaction acting on the reaction canceling magnetic pole units.
The reaction canceling magnetic pole units can be structured so that forces perpendicular to each other in neighboring corners of the armature unit are generated. In such a case, the force to cancel the reaction acting on the stator can be easily calculated.
From a second aspect, the present invention is a method of making a stage unit comprising a process to provide a driving unit including the mover and the stator; and a process to provide the reaction canceling mechanism to apply the force canceling the reaction, which is induced by the driving of the mover and is acting on the stator, to the stator by the electromagnetic interaction. According to this, by providing the driving unit and the reaction canceling mechanism and combining these and other elements mechanically, electrically, and optically as the need arises, the first stage unit of the present invention is made.
From a third aspect, the present invention comprises the armature unit including a plurality of armature coils, which are arranged in the shape of a matrix on the predetermined plane and whose current paths are almost parallel to the predetermined plane; the magnetic pole unit having a plurality of magnets magnetized in directions not perpendicular to the predetermined plane and two-dimensionally generating an alternating magnetic field with a period of 4P/3 in two axis-directions perpendicular to each other practically without generating any magnetic field in an area opposite to the armature unit; and a current driving unit to move the magnetic pole unit relatively to the armature unit in a plane parallel to the predetermined plane by supplying currents to the armature coils respectively. Hereinafter, this stage unit is referred to as a xe2x80x9csecond stage unit of the present inventionxe2x80x9d.
According to this, in making a steady magnetic circuit having a low magnetic resistance, the magnetic pole unit is composed only of the aforementioned magnets without using other magnetic members than the magnets, thereby realizing the light weight of the mover. Accordingly, the driving force of the mover can be reduced and the reaction acting on the stator can be reduced, thereby the vibration of the stator can be decreased and highly accurate positioning can be realized while moving a placed sample at a high speed.
The second stage unit of the present invention can further comprise a magnetic member supporting the armature coils in a side opposite to the magnetic pole unit. In such a case, a magnetic circuit is structured through the magnetic pole unit and the magnetic member, thereby a steady magnetic circuit having a low magnetic resistance can be structured. Therefore, a magnetic flux having high flux density can be generated in the positions of the armature coils. Incidentally, as a material for the magnetic member, one having high electric resistance, high saturation magnetic flux density, low magnetic hysteresis, and low coercive force is preferred.
Also, the second stage unit of the present invention can further comprise a flat-plate-like shaped member disposed between the armature unit and the magnetic pole unit and made of a non-magnetic and non-conductive material. In such a case, when structuring the magnetic pole unit so that it is not contacting the armature unit by an air-bearing system, an air blown out of the magnetic pole unit is blown on the flat-plate-like shaped member, thereby the magnetic pole unit and the flat-plate-like shaped member, eventually the armature unit can be non-contacting each other. Furthermore, because the flat-plate-like shaped is non-magnetic and non-conductive, the magnetic flux generated by the magnetic pole unit is not affected. Accordingly, an easy implementation of relative movement at high speed by a small driving force is possible. Incidentally, a non-magnetic material means a material having magnetic permeability small enough compared with a magnetic material such as iron, etc. and almost equal to that of the air. Furthermore, a non-conductive material means a material having conductance small enough compared with a conductive material such as copper, etc. and almost equal to that of the air.
Furthermore, the second stage unit of the present invention can be so structured that the current driving unit supplies currents for the respective armature coils independently. In such a case, the value and direction of each of currents supplied for the respective armature coils can be controlled independently, thereby the magnetic pole unit and the armature unit can be relatively moved in a predetermined direction.
Furthermore, the second stage unit of the present invention comprises a position detection system to detect the positional relation between the magnetic pole unit and the armature unit; and a control unit (controller) to control at least one of the value and direction of each of currents supplied for the respective armature coils via the current driving unit based on detection results by a position detection. In such a case, the relative position and the relative speed between the magnetic pole unit and the armature unit can be controlled by controlling the value and direction of the respective currents flowing in the armature coils based on position information (speed information) obtained by the position detection system with respect to the magnetic pole unit and the armature unit.
The second stage unit comprising the position detection system and the control unit described above is so structured that the control unit selectively supplies currents for the armature coils opposite with the magnetic pole unit. In such a case, with not supplying currents for armature coils in which no or just weak Lorentz force is induced, efficient current supply is possible and current dissipation can be reduced while maintaining the driving force.
From a fourth aspect, the present invention is a making method comprising a process to provide the armature unit including a plurality of armature coils having a current path almost parallel to the predetermined plane and being arranged in the shape of a matrix on the predetermined plane; a process providing the magnetic pole unit having a plurality of magnets magnetized in directions not perpendicular to the predetermined plane and two-dimensionally generating an alternating magnetic field with a period of 4P/3 in two axis-directions perpendicular to each other practically without generating any magnetic field in an area opposite to the armature unit; and a process providing a current driving unit to move the magnetic pole unit relatively to the armature unit in a plane parallel to the predetermined plane by supplying currents for the armature coils respectively. According to this, by providing the armature unit, the magnetic pole unit and the driving unit, and then combining and adjusting these and other elements mechanically, electrically, and optically as the need arises, the second stage unit of the present invention is made.
In this case, furthermore, it is possible to include a process to provide the position detection system to detect a positional relation between the magnetic pole unit and the armature unit; and a process to provide the control unit to control at least one of the value and direction of each of currents supplied for the respective armature coils through the current driving unit based on detection results by a position detection. In such a case, a stage unit, in which the relative position and the relative speed between the magnetic pole unit and the armature unit can be controlled, can be made.
Incidentally, needless to say, both the first stage unit and the second stage unit can be applied to one stage unit. In such a case, the reaction can be accurately canceled as well as reducing the reaction acting on the stator by, for example, decreasing the driving force of the magnetic pole unit as a mover.
Furthermore, by applying both the making method of the first stage unit and that of the second stage unit to the making of one stage unit, a stage unit to which both the first stage unit and the second stage unit are applied can be made.
From a fifth aspect, out of exposure apparatuses that expose the substrate by irradiating an energy beam and transfer a predetermined pattern onto the substrate, the present invention is an exposure apparatus having a feature of comprising a stage unit as a position control unit to control the position of the substrate.
According to this, by exposing the substrate placed on the stage unit of the present invention, a move at a high speed and highly accurate control of position of the substrate are possible, and both the through-put and the accuracy of exposure can be improved.
From a sixth aspect, out of making methods of an exposure apparatus that exposes a substrate by irradiating an energy beam and transfers an predetermined pattern onto the substrate, the present invention is a method of making the stage unit by providing the driving unit including the mover and the stator, and the reaction canceling mechanism to apply the force canceling the reaction, which is induced by the driving of the mover and is acting on the stator, to the stator by the electromagnetic interaction; and an exposure apparatus making method including the disposing of the stage unit as a position control apparatus to control the position of the substrate. According to this, an exposure unit comprising the first stage unit of the present invention as a position control apparatus to control the position of the substrate is made.
From a seventh aspect, out of making methods of an exposure apparatus that exposes a substrate by irradiating an energy beam and transfers an predetermined pattern onto the substrate, the present invention is a method of making the stage unit by providing the armature unit including a plurality of armature coils that are arranged in the shape of a matrix on the predetermined plane and have current paths almost parallel to the predetermined plane, the magnetic pole unit having a plurality of magnets magnetized in directions not perpendicular to the predetermined plane and two-dimensionally generating an alternating magnetic field with a period of 4P/3 in two axis-directions perpendicular to each other, between the armature coils and itself, practically without generating any magnetic field in an area opposite to the armature unit, and the current driving unit to move the magnetic pole unit relatively to the armature unit in a plane parallel to the predetermined plane by supplying currents for the armature coils respectively; and an exposure apparatus making method including the disposing of the stage unit as a position control apparatus to control the position of the substrate. According to this, an exposure unit comprising the second stage unit of the present invention as a position control apparatus to control the position of the substrate is made.
Incidentally, needless to say, an exposure apparatus can be structured which comprises a stage unit, to which both the first stage unit and the second stage unit of the present invention are applied, as a position control apparatus to control the position of the substrate. In such a case, both the through-put and the accuracy of exposure can be improved.
Furthermore, by applying both the making method of an exposure apparatus comprising the first stage unit and the making method of an exposure apparatus comprising the second stage unit of the present invention to the making of one exposure apparatus, an exposure apparatus can be made which comprises a stage unit to which both the first stage unit and the second stage unit of the present invention are applied.